All self-extinguishing resins which are so far used or described show essential disadvantages. Halogen-containing resins are self-extinguishing but when burning, they develop highly toxic and corrosive flue gases, or they even split off toxic compounds during their preparation. The use of other flame retardants did not so far give satisfactory results neither. Either they are to be used in such important amounts that their properties are impaired or the workability is endangered. In some cases the obtained resins are thermically unstable, or they are water-sensitive, or they are toxically doubtful, or they show other disadvantages. On the other hand, plastics which are less combustible and therefor are requiring lower amounts of additives, such as for example phenol formaldehyde resins, originally show many disadvantages, such as for example poorer mechanical and electrical properties. During curing, these duroplastic resins split off volatile products and therefor are not suitable for many processing methods. Finally, there are some high-tailored plastics which in view of their difficult manufacturing are not suitable for a more general use just for commercial reasons.
Despite very intense efforts, it did not succeed so far to develop a difficultly inflammable, toxically undoubtful polymeric resin which meets all other properties requirements, workability and economy, and which could replace halogen-containing systems.